Copper fluoride based nanocomposites as electrode materials

ABSTRACT

The present invention relates to primary and secondary electrochemical energy storage systems, particularly to such systems as battery cells, which use materials that take up and release ions as a means of storing and supplying electrical energy.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/700,906, filed on Apr. 30, 2015, which is a continuation of U.S.patent application Ser. No. 11/177,729, filed on Jul. 8, 2005, whichclaims the benefit of priority of U.S. Provisional Application No.60/680,253, filed on May 11, 2005. U.S. patent application Ser. No.11/177,729 is a continuation-in-part of U.S. patent application Ser. No.10/721,924, filed on Nov. 25, 2003, which issued as U.S. Pat. No.7,371,338 on May 13, 2008, which claims the benefit of priority of U.S.Provisional Application No. 60/429,492 filed on Nov. 27, 2002. U.S.patent application Ser. No. 10/721,924 is a continuation-in-part of U.S.patent application Ser. No. 10/261,863, filed on Oct. 1, 2002, whichissued as U.S. Pat. No. 7,625,671 on Dec. 1, 2009. The entiredisclosures of U.S. patent application Ser. No. 14/700,906, U.S. patentapplication Ser. No. 11/177,729, U.S. patent application Ser. No.10/721,924, U.S. patent application Ser. No. 10/261,863 and U.S.Provisional Patent Application Nos. 60/429,492 and 60/680,253 areincorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to primary and secondary electrochemicalenergy storage systems, particularly to such systems as battery cells,which use materials that take up and release ions as a means of storingand supplying electrical energy.

BACKGROUND OF THE INVENTION

The lithium-ion battery cell is the premiere high-energy rechargeableenergy storage technology of the present day. Unfortunately, its highperformance still falls short of energy density goals in applicationsranging from telecommunications to biomedical. Although a number offactors within the cell contribute to this performance parameter, themost crucial ones relate to how much energy can be stored in theelectrode materials of the cell.

During the course of development of rechargeable electrochemical cells,such as lithium (Li) and lithium-ion battery cells and the like,numerous materials capable of reversibly accommodating lithium ions havebeen investigated. Among these, occlusion and intercalation materials,such as carbonaceous compounds, layered transition metal oxide and threedimensional pathway spinels have proved to be particularly well-suitedto such applications. However, even while performing reasonably well inrecycling electrical storage systems of significant capacity, many ofthese materials exhibit detrimental properties, such as marginalenvironmental compatibility and safety, which detract from the ultimateacceptability of the rechargeable cells. In addition, some of the morepromising materials are available only at costs that limit widespreaduse. However, of most importance is the fact that the present state ofthe art materials have the capability to store relatively low capacityof charge per weight of material (specific capacity, mAh/g) or energyper weight (specific energy, Wh/kg).

Materials of choice in the fabrication of rechargeable battery cells,particularly highly desirable and broadly implemented Li-ion cells, havefor some considerable time centered upon graphitic negative electrodecompositions, which provide respectable capacity levels in the range of300 mAh/g. Complementary positive electrode materials in present cellsuse less effective layered intercalation compounds, such as LiCoO₂,which generally provides capacities in the range of 150 mAh/g.Alternative intercalation materials, such as LiNiO₂, and LiMn₂O₄, havemore recently gained favor in the industry, since, although exhibitingno appreciable increase in specific capacity, these compounds areavailable at lower cost and provide a greater margin of environmentalacceptability.

Due to increasing demand for ever more compact electrical energy storageand delivery systems for all manner of advancing technologies, thesearch continues for battery cell materials capable of, on the one hand,providing greater specific capacity over wider ranges of cycling rates,voltages, and operating temperatures, while, on the other hand,presenting fewer environmental hazards and greater availability at lowerprocessing and fabrication costs. Searches for more effective positiveelectrode materials, in particular, have become far-reaching withattention turning more frequently to the abundant lower toxicitytransition metal compounds, which are typically accessible at economicalcosts.

In the intense search of material systems which can deliver much higherspecific capacities and energy, interest has shifted to examination ofthe more active fluoride compounds. Recently, Badway et al. (Journal ofthe Electrochemical Society, 150(9) A1209-A1218 (2003)) reported the useof carbon metal fluoride nanocomposites to enable the electrochemicalactivity of metal fluorides. Their studies have shown that reducing theparticle size of metal fluoride to the nanodimensions in combinationwith highly conductive carbon resulted in the enablement of a new metalfluoride conversion process positive electrodes resulting in a majorimprovement in specific capacity relative to current state of the art.Badway et al. reported >90% recovery of the FeF₃ theoretical capacity(>600 mAh/g mAh/g) in the 4.5-1.5 V region through reversibleconversion, which is fundamentally different energy storage mechanismcompared with the present state of the art intercalation.

Despite this success, the full utilization of certain metal fluorides,such as copper fluoride, has not been realized. Researchers have triedto enable this high energy density compound for more than 30 years withonly limited success because of poor utilization of the material. Copperfluoride has a theoretical conversion potential of approximately 3.2 V,and a discharge specific capacity of approximately 520 mAh/g, leading toan exceptionally high energy density in excess of 1500 Wh/kg. Suchcapacity values are over 300% higher than those attained in present daystate-of-the-art rechargeable Li battery cells based on LiCoO₂intercalation compounds. With respect to existing primary cathodecompounds, copper fluoride would exceed the widely utilized MnO₂ energydensity by almost a factor of two.

Hence, there is a need in the art for electrical energy-storage anddelivery systems that utilize copper fluoride effectively.

SUMMARY OF THE INVENTION

The present invention relates to the formation and utilization ofnanostructures of copper fluoride which include metal oxide composites,or nanocomposites; novel copper fluoride structures; and novelconducting matrices. The nanostructures serve as active electrodecomponent materials for use in electrochemical cells, such as lithiumbattery cells, capable of exhibiting high specific capacity at highrecharge and/or discharge rates.

An embodiment of the present invention provides a composition includinga copper fluoride compound nanocomposite as an electrode material for anelectrochemical energy storage cell.

Another embodiment of the present invention provides a compositionhaving crystallites with sizes in the range of about 1 nm to about 100nm, in which the crystallites include a copper fluoride compoundincorporated in a nanocomposite. The aforementioned nanocomposite may beof nanoparticle (1-100 nm), macroparticle sizes (>100 nm), or in theform of a densified thin (<25000 nm) or thick (>25000 nm) films.

A further embodiment of the invention provides a composition includinggreater than 50 weight % of CuF₂ and having X-ray diffraction peaks of(200) and (022) with a 2θ separation less than 0.8 degree, wherein thecomposition demonstrates a specific capacity of about 100 mAh/g to about600 mAh/g at a voltage of about 2 volts to about 4 volts when comparedto a Li/Li⁺ reference potential.

Another embodiment of the invention provides a compound including copperfluoride, wherein the compound includes an x-ray diffraction latticeparameter, a=3.25 Å; b=4.585 Å±0.2 Å; c=4.585 Å±0.2 Å, B=84°±5°.

A further embodiment of the invention provides a nanocomposite compoundincluding copper fluoride, wherein the compound includes an x-raydiffraction lattice parameter, a=3.25 Å±0.2 Å; b=4.585 Å±0.2 Å; c=4.585Å±0.2 Å, B=84°±5°.

Another embodiment of the present invention provides a copper fluoridecompound nanocomposite having greater than 50 weight % of CuF₂ thatexhibits X-ray diffraction peaks (200) and (022) with a 2θ separation ofless than 0.8 degree, prepared by a method including the steps of: (a)combining copper fluoride and a conductive matrix; and (b) fabricatingthe copper fluoride and the conductive matrix into a nano composite.

A further embodiment of the present invention provides a conductivematrix including MoO_(x)F_(z), wherein x is 0≦x≦3 and z is 0≦z≦5combined in such a way that the effective charge on the Mo cation is notmore than 6+.

Another embodiment of the invention provides a MoO_(x)F_(z) conductivematrix wherein x is 0≦x≦3 and z is 0≦z≦5 combined in such a way that aneffective charge on the Mo cation is not more than 6y+, prepared by themethod including the steps of: (a) combining copper fluoride and aconductive matrix; (b) fabricating said copper fluoride and saidconductive matrix into a nanocomposite.

A further embodiment of the invention provides an electrochemical cellincluding (a) a negative electrode; (b) a positive electrode comprisinga copper fluoride compound nanocomposite; and (c) a separator disposedbetween the negative and positive electrodes.

Still another embodiment provides a method of preparing a copperfluoride compound nanocomposite having greater than 50 weight % of CuF₂and having X-ray diffraction peaks of (200) and (022) with a two-thetaseparation of less than 0.8 degree, the method including the steps of:combining copper fluoride and a conductive matrix; and fabricating thecopper fluoride and the conductive matrix into a nanocomposite.

A further embodiment provides a composition including a copper fluoridecompound nanocomposite demonstrating a specific capacity of about 100mA/g to about 600 mAh/g at a voltage of about 2 volts to about 4 voltswhen compared to a Li/Li+ reference potential.

A further embodiment of the invention provides an electrochemical cellincluding: (a) a negative electrode; (b) a positive electrode having acopper fluoride compound nanocomposite; and (c) a separator disposedbetween the negative and positive electrodes, wherein theelectrochemical cell demonstrates a specific capacity of about 100 mAh/gto about 600 mAh/g at a voltage of about 2 V to about 5 V.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a graph depicting voltage as a function of specific capacityfor a non-nanocomposite CuF₂ and a copper fluoride nanocomposite.

FIG. 2 is a graph depicting the specific capacity of a copper fluoridenanocomposite with a carbon conductive matrix, at various processingconditions.

FIG. 3 is a graph depicting the specific capacity of a non-nanocompositeCuF₂ with a 50 weight % MoO₃ conductive matrix.

FIG. 4 is a graph depicting voltage as a function of specific capacityfor a copper fluoride nanocomposite with a 25 weight % MoO₃ conductivematrix.

FIG. 5 is a graph depicting voltage as a function of specific capacityfor a copper fluoride nanocomposite with a 15 weight % MoO₃ conductivematrix.

FIG. 6 is a graph depicting voltage as a function of specific capacityfor a copper fluoride nanocomposite with a 7 weight % MoO₃ conductivematrix.

FIG. 7 is a graph depicting voltage as a function of specific capacityfor a copper fluoride nanocomposite with varying amounts of MoO₃ and acopper fluoride nanocomposite with a carbon conductive matrixdemonstrating the specific advantage of a metal oxide/oxyfluoridematrix.

FIG. 8 is a graph depicting voltage as a function of specific capacityfor a copper fluoride nanocomposite of the invention with 15 weight %VO₂ conductive matrix.

FIG. 9 shows X-ray diffraction data of a novel copper fluoride structurefabricated with CuF₂ and a MoO₃ conductive matrix and a copper fluoridenanocomposite fabricated with carbon.

FIG. 10 depicts Bragg reflection peaks characterizing a novel copperfluoride structure.

FIG. 11 depicts Bragg reflection peaks of copper fluoride with carbonnanocomposites, and nanocomposites of copper fluoride with metaloxygen-anion-containing conductive matrices.

FIG. 12 depicts Bragg reflection peaks of copper fluoride and carbonnanocomposites under a wide variety of nanocomposite formationconditions and post fabrication thermal anneals.

FIG. 13 depicts Bragg reflection peaks of copper fluoride and carbonnanocomposites, and copper fluoride and CuO nanocomposites.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides improved materials for batterycomponents, specifically for positive electrodes in primary andrechargeable battery cells.

In one embodiment, the present invention provides a compositionincluding a copper fluoride compound nanocomposite demonstrating aspecific capacity of about 100 mAh/g to about 600 mAh/g at a voltage ofabout 2 V to about 4 V when compared to a Li/Li+ reference potential. Ina preferred embodiment, the demonstrated specific capacity is from about300 mAh/g to about 500 mAh/g. In a more preferred embodiment, thedemonstrated specific capacity is from about 400 mAh/g to about 500mAh/g. As used herein, “specific capacity” refers to the amount ofenergy the copper fluoride compound nanocomposite contains in milliamphours (mAh) per unit weight.

In one embodiment, the specific capacity of the copper fluoride compoundnanocomposite is reversible. “Reversible specific capacity” means thatthe nanocomposite of the present invention may be recharged by passing acurrent through it in a direction opposite to that of discharge.

The phrase “copper fluoride compound nanocomposites” as used hereinmeans nanocrystallites comprising at least a “copper fluoride compound”incorporated within a nanocomposite, which may or may not be ofnanoparticle size. As used herein, the phrase “copper fluoride compoundincludes any compound that comprises the elements of copper (Cu) andfluorine (F). Examples of copper fluoride compounds include, but are notlimited to, CuF₂.

Preferably, the copper fluoride compound nanocomposite further includesa second metal. One of skill in the art can readily identify metals foruse in copper fluoride compound nanocomposites of the present invention.Such metals include, but are not limited to, non-transition metals andtransition metals, preferably transition metals, and more preferablyfirst row transition metals. Specific examples of metals for use incopper fluoride compound nanocomposites of the present inventioninclude, but are not limited to, Fe, Co, Ni, Mn, V, Mo, Pb, Sb, Bi, Sn,Nb, Ag, Cr and Zn.

In a preferred embodiment, when a second metal is included in the copperfluoride nanocomposite of the invention, the compound is of the formulaCu_(x),Me_(y)F, where Me is the second metal where x>y.

In another embodiment, the copper fluoride compound further includesoxygen. One of skill in the art will recognize that oxygen cansubstitute for fluorine in metal fluorides. Oxygen may act tosignificantly improve the electrical conductivity of the nanocompositeof the invention.

In yet another embodiment, both oxygen and a second metal are includedin the copper fluoride compound nanocomposite of the present invention.In a preferred embodiment, the compound is of the formulaCu_(x)Me_(y)F_(z)O_(w), wherein x+z>y+w and w>0.

Carbon may, optionally, be included in the copper fluoride compoundnanocomposite of the present invention. Preferably, less than 50 weight% of carbon is used. More preferably, less than 25 weight % carbon isused. Even more preferably less than 5 weight % carbon is used. Yet,still more preferably, the copper fluoride compound nanocomposite is ofthe formula Cu_(x)Me_(y)F_(z)O_(w)C, wherein x+z>y+w and w>0.

The copper fluoride compound nanocomposites of the present inventionmay, yet, further include a conductive matrix. As used herein, a“conductive matrix” refers to a matrix that includes conductivematerials, some of which may be ionic and/or electronic conductors.Preferably the matrix will retain both ionic and electronicconductivity; such materials are commonly referred to as “mixedconductors”.

Suitable conductive matrices include, but are not limited to, VO₂, MoO₂,NiO, MoO₃, molybdenum sulfides, molybdenum oxysulfides, titaniumsulfide, MoO_(x)F_(z), wherein x is 0≦x≦3 and z is 0≦z≦5 combined insuch a way that the effective charge on the Mo cation is not more than6+, V₂O₅, V₆O₁₃, CuO, MnO₂, chromium oxides, and carbon fluorides, forexample, CF_(0.8).

The copper fluoride compound nanocomposite of the present inventionincludes, preferably, from about 1 to about 50 weight % of a conductivematrix. In another, preferred, embodiment, the copper fluoride compoundnanocomposite of the present invention includes from about 1 to about 25weight % of a conductive matrix. Even more preferably, the copperfluoride compound nanocomposite of the present invention includes fromabout 2 to about 15 weight % of a conductive matrix.

Preferably, the conductive matrix is MoO_(x)F_(z) where x is 0≦x≦3 and zis 0≦z≦5 combined in such a way that the effective charge on the Mocation is not more than 6+. Even more preferably, the conductive matrixis MoO₃ or MoF₃.

In another embodiment, the copper fluoride compound nanocomposite of thepresent invention includes from about 1 to about 50 weight % ofMoO_(x)F_(z). Preferably, the nanocomposite includes from about 2 toabout 25 weight % of MoO_(x)F_(z). Even more preferably, thenanocomposite of the present invention includes from about 2 to about 15weight % of MoO_(x)F_(z).

The copper fluoride compound nanocomposites of the present inventionpreferably have a crystallite size of about 1 nm to about 100 nm indiameter; more preferably, of about 1 nm to about 50 nm in diameter;even more preferably of about 2 nm to about 30 nm in diameter; and stillmore preferably, of about 2 nm to about 15 nm in diameter.

The inventive nanocomposites may be prepared by extreme, highimpact-energy milling of a mixture that includes a copper fluoridecompound and, optionally, a metal and/or carbon and/or oxygen and/or 5to 50 weight % of a conductive matrix. Thus, the copper fluoridecompound nanocomposite of the present invention can be prepared by usingan impact mixer/mill such as the commercially available SPEX 8000 device(SPEX Industries, Edison N.J., USA). Unlike the shearing action ofconventional planetary, roller, or ball mills, which at best may allowfor size reduction of crystallite particles to the micrometer range, theextremely high-energy impact action impressed upon the component mixtureby the impact mill provides, within milling periods as short as about 10minutes, a particle size reduction of the processed material to thenanostructure range of less than about 100 nm. Further milling for aslittle as 30 minutes up to about 4 hours brings aboutcrystallite-particle size reduction to less than about 40 nm.

Other methods may be used to form the nanocomposites of the presentinvention. As will be evident to a skilled artisan, solution or geltechniques may be used to fabricate the nanocomposites. Generally, asused herein, solution, gel, or high-energy impact milling techniques arereferred to as “nanocomposite fabrication methods.”

When copper fluoride is milled with another component, the copperfluoride undergoes chemical changes such that its X ray diffractioncharacteristics takes on the character of a new, highlyelectrochemically active material, although retaining major aspects ofthe copper fluoride. In addition, the nanocrystallite formation can becharacterized easily by well known methods such as Bragg peak broadeningin x-ray diffraction and microscopy by methods such as transmissionelectron microscopy.

In another aspect of the present invention, an electrochemical cell,preferably a primary or rechargeable battery cell, is provided whichemploys the inventive copper fluoride compound nanocomposites as thecathode material. The cell may be prepared by any known method. Theinventive nanocomposite electrode (cathode) materials function well withmost other known primary or secondary cell composition components,including polymeric matrices and adjunct compounds, as well as withcommonly used separator and electrolyte solvents and solutes.

For example, electrolyte compositions commonly used in knownrechargeable electrochemical-cell fabrication serve equally well in thecells of the present invention. These electrolyte compositions mayinclude one or more metallic salts, such as, but not limited to,lithium, magnesium, calcium, zinc, manganese, and yttrium. Lithiumsalts, such as LiPF₆, LiBF₄, LiClO₄, and the like, dissolved in commoncyclic and acyclic organic solvents, such as ethylene carbonate,dimethyl carbonate, propylene carbonate, ethyl methyl carbonate, andmixtures thereof, may be used. As with optimization of thenanocomposites of the present invention, specific combinations ofelectrolyte components will be a matter of preference of the cellfabricator and may depend on an intended use of the cell, althoughconsideration may be given to the use of solutes such as LiBF₄, whichappear less susceptible during cell cycling to hydrolytically formingHF, which could affect the optimum performance of some metal fluorides.For such reason, for instance, a LiBF₄:propylene carbonate electrolytemay be preferred over one comprising a long-utilized standard solutionof LiPF₆ in a mixture of ethylene carbonate:dimethyl carbonate. Inaddition, such nanocomposites may be incorporated into solid statepolymer cells utilizing solid state ionically conducting matricesderived from compounds such as polyethylene oxide (PEO). Nanocompositesalso may be fabricated by thin film deposition techniques and beincorporated into solid state thin film lithium batteries utilizing aglassy electrolyte. Finally, such electrode materials may beincorporated into cells utilizing ionic liquid solvents as theelectrolytes.

Likewise, the negative electrode members of electrochemical cells mayadvantageously include any of the widely used known ion sources such aslithium metal and lithium alloys, such as those comprised of lithiumtin, lithium silicon, lithium aluminum, lithiated carbons such as thosebased on coke, hard carbon, graphite, nanotubes or C₆₀, and lithiatedmetal nitrides. The negative electrode members of electrochemical cellsalso may further include either a magnesium-, calcium-, zinc-,manganese-, or yttrium-based negative electrode.

In another aspect of the present invention, the copper fluoride compoundnanocomposite of the present invention is characterized by three (Bragg)X-ray diffraction peaks, with 2θ values between 52 and 59 degrees. Incontrast, the X-ray diffraction (XRD) characteristics of milled CuF₂exhibits four XRD peaks (1, 2, −1), (2, 1, −1), (002), and (220). Thenanocomposite of the present invention will also be referred to hereinas the “three-peaks” copper fluoride compound nanocomposite formed bythe systematic coalescence of the (200) and (022) XRD peak.

In another embodiment the copper fluoride compound is characterized byan x-ray diffraction lattice parameter wherein a=3.25 Å±0.2 Å; b=4.585Å±0.2 Å; c=4.585 Å±0.2 Å, B=84°±5°.

In another embodiment, the nanocomposite of the present inventionincludes a copper fluoride compound and the copper fluoride compound iscategorized by an X-ray diffraction lattice parameter wherein a=3.25Å±0.2 Å; b=4.585 Å±0.2 Å; c=4.585 Å±0.2 Å, B=84°±5°.

In another embodiment of the present invention, the three-peaks copperfluoride compound nanocomposite has a composition that includes greaterthan 50 weight % of copper fluoride. The (200) and (022) XRD peaks havea 2θ separation of less than 0.8 degree.

A three-peaks copper fluoride compound nanocomposite includes anycompound that has among its constituents the elements of copper (Cu) andfluorine (F). Examples of copper fluoride compounds include, but are notlimited to, CuF₂. According to an aspect of the embodiment, thethree-peaks copper fluoride compound nanocomposite exhibits a specificcapacity of about 100 mA/g to about 600 mA/g at a voltage of about 2 Vto about 5 V. In a preferred embodiment, the specific capacity is fromabout 400 mA/g to about 500 mAh/g.

In another embodiment, the specific capacity of the three-peaks copperfluoride compound nanocomposite is reversible. This means that it isrechargeable upon a charge in the direction of a current passed throughthe nanocomposite.

Preferably, the three-peaks copper fluoride compound nanocompositefurther includes a second metal. Such metals include, but are notlimited to, non-transition metals and transition metals, preferablytransition metals, and more preferably first row transition metals.Specific examples of metals for use with the three-peaks copper fluoridecompound nanocomposite of the present invention include, but are notlimited to, Fe, Co, Ni, Mn, V, Mo, Pb, Sb, Bi, Cr, Nb, Ag and Zn.

In another embodiment, carbon is included in the three-peaksnanocomposite of the present invention. Preferably, the nanocompositeincludes less than 50 weight % of carbon.

In another embodiment, oxygen is included in the three-peaksnanocomposite of the present invention.

In another embodiment, the three-peaks copper fluoride compoundnanocomposite of the present invention may include a conductive matrix.

Suitable conductive matrices include, but are not limited to, NiO, MoO₃,molybdenum sulfides, molybdenum oxysulfides, titanium sulfide,MoO_(x)F_(z), wherein x is 0≦x≦3 and z is 0≦z≦5 combined in such a waythat the effective charge on the Mo cation is not more than 6+, V₂O₅,V₆O₁₃, CuO, MnO₂, chromium oxides and carbon fluorides, for example,CF_(0.8), VO₂, MoO₂. The three-peaks copper fluoride compoundnanocomposite of the present invention includes, preferably, from about5 to about 50 weight % of a conductive matrix. In another, preferred,embodiment, the inventive three-peaks copper fluoride compoundnanocomposite includes from about 5 to about 25 weight % of a conductivematrix. Even more preferably, the three-peaks copper fluoride compoundnanocomposite of the present invention includes from about 7 to about 15weight % of a conductive matrix.

Preferably, the conductive matrix is MoO_(x)F_(z) wherein x is 0≦x≦3 andz is 0≦z≦5 combined in such a way that the effective charge on the Mocation is not more than 6+. Even more preferably, the conductive matrixis MoO₃. The three-peaks copper fluoride compound nanocomposite of thepresent invention includes, from about 1 to about 50 weight %MoO_(x)F_(z). Preferably, the nanocomposite includes from about 2 toabout 25 weight % of MoO_(x)F_(z). Even more preferably, the three-peakscopper fluoride compound nanocomposite of the present invention includesfrom about 2 to about 15 weight % of MoO_(x)F_(z).

The three-peaks copper fluoride compound nanocomposite preferablyincludes copper fluoride, with crystallite sizes of about 1 nm to about100 nm in diameter, more preferably of about 1 nm to about 50 nm indiameter, even more preferably of about 2 nm to about 30 nm in diameter,and still more preferably of about 2 nm to about 15 nm in diameter.

In another aspect of the present invention, an electrochemical cell,preferably a primary or rechargeable battery cell, is provided whichemploys a three-peaks copper fluoride compound nanocomposite as thecathode material. The cell may be prepared by any known method. Thethree-peaks copper fluoride compound nanocomposite electrode (cathode)materials function well with most other known primary or secondary cellcomposition components, including polymeric matrices and adjunctcompounds, as well as with commonly used separator and electrolytesolvents and solutes.

In another aspect of the present invention, a copper fluoride compoundnanocomposite having greater than 50 weight % CuF₂ and having (200) and(022) XRD peaks with a 2θ separation of 0.8 degree is prepared by amethod including the steps of (a) combining copper fluoride and aconductive matrix; and (b) fabricating the copper fluoride and theconductive matrix into a nanocomposite by any suitable known method forforming nanocomposites. Preferably, the method is the high-energy impactmilling method described above. A suitable conductive matrix may be oneselected from VO₂, MoO₂, MoO₃, V₂O₂, CuO, CF_(0.8) and MoO_(x)F_(z).Preferably, the conductive matrix is MoO_(x)F_(z) wherein x is 0≦x≦3 andz is 0≦z≦5 combined in such a way that the effective charge on the Mocation is not more than 6+ or MoO₃.

Metal fluorides may be combined with the inventive conductive matrix.Suitable metals useful in metal fluorides include, but are not limitedto, non-transition metals and transition metals, preferably transitionmetals, more preferably, first row transition metals. Specific examplesof metals for use with the metal fluorides of the conductive matrix ofthe present invention include, but are not limited to, Fe, Co, Ni, Mn,Cu, V, Mo, Sn, Pb, Sb, Bi, Ag and Si. Preferably, Cu is used.

In one embodiment, a MoO_(x)F_(z) conductive matrix used to fabricate ananocomposite includes at least one metal fluoride. Preferably, thenanocomposite includes from about 5 to 50 weight % MoO_(x)F_(z), morepreferably from about 5 to about 25 weight % MoO_(x)F_(z) and even morepreferably from about 7 to about 15 weight % MoO_(x)F_(z).

Carbon may, optionally, be included in the MoO_(x)F_(z) conductivematrix of the present invention. Preferably, less than 50 weight %carbon is used. More preferably, less than 15 weight % of carbon isused.

The MoO_(x)F_(z) conductive matrix of the present invention preferably,has a particle size of about 1 nm to about 100 nm. More preferably, thecrystallite size is about 1 nm to about 50 nm, and even more preferablythe crystallite size is about 2 nm to about 30 nm. Still morepreferably, the particle size is about 2 nm to about 15 nm.

The inventive conductive matrix may be prepared by extreme, high-impactenergy milling, as described above.

In another aspect of the present invention, an electrochemical cell,preferably a primary or rechargeable battery cell, is provided, whichemploys the inventive conductive matrix as a cathode material,optionally employing one or more of the metal fluorides described above.The cell may be prepared by any suitable method known in the art. Theconductive matrix electrode (cathode) material functions well with mostother known primary or secondary cell composition components, includingpolymeric matrices and adjunct compounds, as well as with commonly usedseparator and electrolyte solvents and solutes.

Examples

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how tomake and use the present invention, and are not intended to limit thescope of what the inventors regard as their invention nor are theyintended to represent that the experiments below are all or the onlyexperiments performed. Efforts have been made to ensure accuracy withrespect to numbers used (e.g. amounts, temperature, etc.) but someexperimental errors and deviations should be accounted for. Unlessindicated otherwise, parts are parts by weight, molecular weight isweight average molecular weight, temperature is in degrees Centigrade,and pressure is at or near atmospheric.

Example 1 Electrode Preparation

Electrodes were prepared by adding poly-vinylidenefluoride-co-hexafluoropropylene (Kynar 280, Elf Atochem), carbon black(Super P, MMM), and dibutyl phthalate (Aldrich) to the inventivenanocomposites in acetone. The slurry was tape cast, dried for 1 hour at22° C., and rinsed in 99.8% anhydrous ether (Aldrich) to extract thedibutyl phthalate plasticizer. The electrodes, 1 cm² disks or coin cellstypically containing 57+/−1% inventive nanocomposites and 12+/−1% carbonblack, were tested electrochemically versus Li metal (Johnson Matthey).The Swagelok™ or coin cells were assembled in a Helium-filled dry boxusing Whatman GF/D glass fiber separators saturated with 1 M LiPF₆ inethylene carbonate:dimethyl carbonate (EC:DMC 1:1 in vol.) electrolyte(Merck). The cells were controlled by Mac-Pile (Biologic) or Maccorbattery cycling systems. Cells were cycled under a constant current of22 mA/g at 24° C.

Example 2 Preparation of CuF₂ Nanocomposite with MoO₃ Matrix and CuF₂Non-Nanocomposite Reference Material

A sample of 93% weight CuF₂, 15% weight carbon and 7% weight MoO₃ weremilled in a high-energy impact mill under a helium atmosphere for 20min. and subsequently annealed at 200° C. before the sample wasextracted for structural and electrochemical characterization. Theinventive nanocomposite was composed of crystallites of approximately 30nm. As a basis for comparison, CuF₂ was thoroughly mixed underlow-energy shear grinding condition using a mortar and pestle to yield areference electrode material composed of particles with a size of about1000 nm.

Example 3 Specific Capacities of CuF₂ Inventive Nanocomposite and theCuF₂ Non-Nanocomposite Reference Material

Both the inventive nanocomposite and the reference electrode materialwere compared to assess their electrochemical efficacy as electrodematerials. A series of cells was fabricated in the above-describedmanner and tested at room temperature (22° C.) over a period of time atconstant amperage cycles of 22 mA/g between 4.5 and 2.0 V. Thesubstantially insignificant specific capacity of about 100 mAh/g for thereference electrode material mixture may be seen in FIG. 1 whichspecific capacities for a non-nanocomposite CuF₂ and a copper fluoridenanocomposite. As seen in the figure, results of similar testing for theinventive nanocomposite show that the specific capacity of the milledcopper fluoride increased by 400% compared with the reference electrode.

Example 4 Specific Capacity of a CuF₂ Inventive Nanocomposite with aCarbon-Only Matrix

85 weight % CuF₂ and 15 weight % carbon were high-energy milled asdescribed above for varying time periods, anneal temperatures, andanneal times to form a copper fluoride nanocomposite. Electrochemicalcells were fabricated as described above and the specific capacity ofthe copper fluoride nanocomposite was observed. As can be seen in FIG.2, the specific capacity was significantly increased by the millingprocess. However, the observed specific capacities are lower than thetheoretical composite specific capacity of 480 mAh/g.

Example 5 Effect of Varying Amounts of MoO₃ Conductive Matrix on theSpecific Capacity of a CuF₂ Inventive Nanocomposite

MoO₃ was used as a conductive matrix at varying concentrations to assessthe effect of this compound for use with the copper fluoride compoundnanocomposite of the present invention. 50 weight % CuF₂ and 50 weight %MoO₃; 75 weight % CuF₂ and 25 weight % MoO₃; 85 weight % CuF₂; 15 weight% MoO₃, 93 weight % CuF₂, and 7 weight % MoO₃ were high-energy milled asdescribed above for various times and post annealed at varioustemperatures as summarized in FIG. 3 through FIG. 6 and tested forspecific capacity. An electrode with 50 weight % CuF₂ and 50 weight %MoO₃ (FIG. 3) shows a high discharge capacity when compared with thereference CuF₂ electrode material (FIG. 1). However, the specificcapacity is not greatly varied from that of CuF₂ high-energy milled withcarbon (FIG. 2). An electrode with 25 weight % MoO₃ and 75 weight % CuF₂(FIG. 4) is observed to have a greater specific capacity than theelectrode that combines CuF₂ and carbon (FIG. 2) when the materials arepost annealed at 200° C. for several hours. The specific capacity isfurther improved when only 15 weight % MoO₃ is used (FIG. 5). Thespecific capacity is increased even more at 7 weight % MoO₃ (FIG. 6).

As can be seen in FIG. 7, CuF₂ nanocomposites with MoO₃ conductivematrices routinely have specific capacities in excess of 400 mAh/g.These values exceed non-nanostructured CuF₂ (the reference electrodematerial) by a considerable amount as this macro material shows littleelectrochemical activity (FIG. 1). Accounting for the weight of thematrix in the CuF₂ nanocomposite, it is clear that the specific energydensities at greater than 90% of the theoretical energy densities areexceptional. Such calculations assume that MoO₃ is an electrochemicallyactive matrix composition.

Example 6 Effect of VO₂ Conductive Matrix on the Specific Capacity ofCuF₂ Inventive Nanocomposite

15 weight % VO₂ was high-energy milled with 85 weight % CuF₂ and testedfor specific capacity, as described above, to ascertain the effect ofthis conductive matrix. FIG. 8 shows the high discharge specificcapacity of this nanocomposite in comparison with the CuF₂ referenceelectrode material (FIG. 8).

Example 7 Effect of Carbon on the Specific Capacity of the CuMoOFInventive Nanocomposite

As described and shown above, the specific capacities of the CuMoOFnanocomposites of the present invention, were improved by lowering theweight percentages of the MoO₃ matrix component. As the percentages ofmolybdenum and oxygen were decreased, carbon was added to thenanocomposite to improve the uniformity of the inventive nanocomposite.7 weight % MoO₃ and 93 weight % CuF₂ were high-energy milled for 20minutes, followed by another milling for either 10 minutes or 30 minuteswith the addition of 5 weight % SP carbon, a type of networked carbonblack supplied by MMM, Belgium. The samples were annealed at 200° C. fortwo hours at various periods indicated in Table 1. As is evident inTable 1, exemplary specific capacity was observed with the best resultsexceeding 96% utilization of CuF₂, even though carbon was used. Carbonoffers electrical conductivity, but, for the most part, iselectrochemically non-active.

TABLE 1 7 weight % MoO3 + 93 weight % CuF2 5 weight % Post 20 m HEManneal C HEM anneal (2 h) Specific Capacity Temp (° C.) (2 h) time Temp(° C.) mAh/g Composite 200 10 m None 414 200 10 m 200 411 200 30 m None396 200 30 m 200 444 None 10 m None 397 None 10 m 200 403 None 30 m None401 None 30 m 200 448

Example 8 Characterization of Novel Inventive CuF₂ Structure

When 7 weight % MoO₃ and 93 weight % CuF₂ are high-energy milled asdescribed above, a new structural material is observed as shown in FIG.9 and FIG. 10. These figures show the four known Bragg reflectionsassociated with the monoclinic form of cuF₂ (1, 2, −1), (2, 1, −1),(002), and (220), when CuF₂ with 15 weight % carbon is used for thenanocomposite. However, CuF₂ with 7 weight % MoO₃ results in only threepeaks. Particularly, the (002) and (220) peaks coalesce into a combinedpeak when (002) and (220) are almost of the same values (see FIG. 9 andFIG. 10). This result is indicative of a structural transformation ofthe monoclinic lattice from where “b” does not equal “c”, to where “b”approximately equals “c”. This structural transformation is consistentamong all the optimized materials utilizing a matrix that contains anoxygen anion, as shown in the XRD scans of FIG. 11. Without being boundby theory, the metal oxide matrix releases some of its oxygen to thecopper fluoride nanostructure while the metal oxide matrix incorporatesfluorine anions from the copper fluoride in a thermodynamically drivenanion exchange.

The XRD scans of FIGS. 11 and 12 present examples where high-energymilling of CuF₂ with carbon results in the retention of the monoclinicstructure, as previously described for FIG. 9 and FIG. 10. FIG. 12 showsthat under a wide variety of nanocomposite formation conditions and postfabrication thermal anneals, there is a consistent formation of the fourBragg peaks (1, 2, −1), (2, 1, −1), (002), and (220), between the 2θvalues of 52 and 59 degrees. As described above, none of these samplesexhibit the outstanding electrochemical properties of the inventive CuF₂nanocomposites.

To further support the fact that anion substitution is involved with theformation of the novel copper fluoride composition, CuF₂ nanocompositeswere formed with iso-cation CuO materials. FIG. 13 compares thiscomposition with carbon based CuF₂ nanocomposites. The identicalstructural transformation is seen to occur with this material as wasshown with the other metal oxides, described above. The transformationis not due to other cations since Cu was utilized both in the fluorideand the oxide.

While the present invention has been described with respect to what ispresently considered to be the preferred embodiment(s), it is to beunderstood that the invention is not limited to the disclosedembodiment(s). To the contrary, the invention is intended to covervarious modifications and equivalent compositions and/or arrangementsincluded within the spirit and scope of the appended claims. The scopeof the following claims is to be accorded to the broadest interpretationso as to encompass all such modifications and equivalent structures andfunctions.

1. A nanocomposite comprising a copper fluoride compound, wherein thenanocomposite composition is formed of crystallites of about 1 nm toabout 100 nm in diameter.
 2. The nanocomposite according to claim 1,wherein said nanocomposite demonstrates a specific capacity of about 100mAh/g to about 600 mAh/g at a voltage of about 2 volts to about 4 voltswhen compared to a Li/Li+ reference potential.
 3. The nanocompositeaccording to claim 1, wherein the copper fluoride compound comprisesCuF₂.
 4. The nanocomposite according to claim 1, further comprising ametal.
 5. The nanocomposite according to claim 4, wherein the metal isselected from the group consisting essentially of Fe, Co, Ni, Mn, V, Mo,Pb, Sb, Bi, Nb, Zn, Sn, Ag and Cr.
 6. The nanocomposite according toclaim 1, further comprising carbon.
 7. (canceled)
 8. The nanocompositeaccording to claim 1, further comprising oxygen.
 9. The nanocompositeaccording to claim 1, wherein the copper fluoride compound comprisesCu_(x)F_(z)O_(w), wherein z>w and w>0.
 10. The nanocomposite accordingto claim 1, wherein the copper fluoride compound comprisesCu_(x)Me_(y)F_(z)O_(w), wherein Me is a metal and x+z>y+w and w>0. 11.The nanocomposite according to claim 10, wherein Me is a transitionmetal.
 12. The nanocomposite according to claim 10, wherein Me isselected from the group consisting essentially of Fe, Co, Ni, Mn, V, Mo,Pb, Sb, Bi, Nb, Sn, Zn, Ag and Cr.
 13. The nanocomposite according toclaim 1, wherein the copper fluoride compound comprises a compound ofthe formula Cu_(x)Me_(y)F_(z)O_(w), wherein Me is a transition metal andx+z>y+w and w>0.
 14. (canceled)
 15. The nanocomposite of claim 1,wherein the copper fluoride compound comprises a compound of the formulaCu_(x)Me_(y)F_(z)O_(w), wherein x+z>y+w and w>0, and wherein Me isselected from the group consisting essentially of Fe, Co, Ni, Mn, V, Mo,Pb, Sb, Bi, Nb, Zn, Sn, Ag and Cr.
 16. (canceled)
 17. The nanocompositeaccording to claim 1, further comprising a conducting matrix. 18.(canceled)
 19. (canceled) 20-26. (canceled)
 27. A compound comprisingcopper fluoride, wherein the compound comprises an x-ray diffractionlattice parameter, a=3.25 Å±0.2 Å; b=4.585 Å±0.2 Å; c=4.585 Å±0.2 Å,B=84°±5°.
 28. (canceled)
 29. An electrochemical cell comprising: anegative electrode; a positive electrode comprising the nanocomposite ofclaim 1; and a separator disposed between the negative and positiveelectrodes. 30-32. (canceled)
 33. The cell according to claim 29,wherein the nanocomposite comprises CuF₂.
 34. The cell according toclaim 29, wherein the nanocomposite comprises a composition comprisinggreater than 50 weight % CuF₂, and wherein the CuF₂ exhibits X-raydiffraction peaks of (200) and (022) with a 2θ separation of less than0.8 degree.
 35. The cell according to claim 29, wherein thenanocomposite further comprises a metal. 36-52. (canceled)
 53. Thenanocomposite of claim 1, wherein the copper fluoride compound includesCuF₂ and the CuF₂ constitutes greater than 50 weight % of thenanocomposite, and wherein the nanocomposite has X-ray diffraction peaksof (200) and (022) with a 2θ separation less than 0.8 degree, andwherein the nanocomposite demonstrates a specific capacity of about 100mAh/g to about 600 mAh/g at a voltage of about 2 volts to about 4 voltswhen compared to a Li/Li+ reference potential.
 54. The composition ofclaim 1, wherein the composition is present in an electrode of arechargeable battery.